wqrs attempts to locate QRS complexes
in an ECG signal in the specified record. The detector algorithm is based
on the length transform. The output of wqrs is an annotation file (with
annotator name wqrs) in which all detected beats are labelled normal; the
annotation file will also contain optional J-point annotations if the -j
option (see below) is used.

wqrs can process records containing any number
of signals, but it uses only one signal for QRS detection (signal 0 by
default; this can be changed using the -s option, see below). wqrs is optimized
for use with adult human ECGs. For other ECGs, it may be necessary to experiment
with the sampling frequency as recorded in the input record’s header file
(see header(5)
), the detector threshold (which can be set using the -m option),
and the time constants indicated in the source file.

wqrs optionally uses
the WFDB library’s setifreq function to resample the input signal at 120
or 150 Hz (depending on the mains frequency, which can be specified using
the -p option). wqrs performs well using input sampled at a range of rates
up to 360 Hz and possibly higher rates, but it has been designed and tested
to work best on signals sampled at 120 or 150 Hz.

Options include:

-d

Dump
the raw and length-transformed input samples in text format on the standard
output, but do not detect or annotate QRS complexes.

Read the signal files in high-resolution mode (default:
standard mode). These modes are identical for ordinary records. For multifrequency
records, the standard decimation of oversampled signals to the frame rate
is suppressed in high-resolution mode (rather, all other signals are resampled
at the highest sampling frequency).

-j

Find and annotate J-points (QRS ends)
as well as QRS onsets.

-mthreshold

Specify the detection threshold (default:
100 microvolts); use higher values to reduce false detections, or lower
values to reduce the number of missed beats.

-pfrequency

Specify the power
line (mains) frequency used at the time of the recording, in Hz (default:
60). wqrs will apply a notch filter of the specified frequency to the input
signal before length-transforming it.

-R

Resample the input at 120 Hz if the
power line frequency is 60 Hz, or at 150 Hz otherwise (default: do not
resample).